Multi-client ADSL modem

ABSTRACT

A multi-client ADSL modem network ( 10 ) that can be configured for a home or office network when multiple ADSL client modems ( 18 ) are installed in different communication terminals ( 22 ). One ADSL modem ( 14 ) at a central office ( 12 ) coordinates the remote multi-client modems ( 18 ) for communication over a single twisted pair loop carrier phone line ( 16 ), allowing the connected modems ( 18 ) to communicate not only with the CO modem ( 14 ), but also with each other by sharing frames, tones, or by code division techniques on upstream channels. The CO modem ( 14 ) operates as a network hub and/or arbitrator, and facilitates one ADSL modem to become the master modem and maintain the superframe. The present invention provides home network ADSL service without extra wiring or equipment, thus providing a low cost approach for home networking of ADSL service.

PRIORITY

This application claims priority of Provisional U.S. Patent applicationSer. No. 60/156,475 filed Sep. 28, 1999.

FIELD OF THE INVENTION

The present invention is generally related to communication networks,and more specifically to networks adapted to communicate over standardresidential 2-wire phone lines including those adapted to support ADSLcommunications.

BACKGROUND OF THE INVENTION

Asymmetrical Digital Subscriber Lines (ADSL) is an ANSI standardidentified as TI.413 issued in 1995 which presents the electricalcharacteristics of the ADSL signal as it should appear at a networkinterface. Generally, ADSL is a high-speed communication technology thatallows one client modem, such as that at a remote terminal (RT), to beconnected to only one central office (CO) modem through one twisted pairtelephone line forming a loop. Typically, discrete multi-tone (DMT)modulation is the chosen line code technique standard in a typical ADSLsystem. Upstream communications, such as from RT to CO, and downstreamcommunications, such as CO to RT, are divided from one another usingfrequency division multiplexing (FDM) or using echo canceling, allowingthe frequency band for upstream communications to be shared withdownstream communications thereby increasing the overall data rate overthe loop.

Disadvantageously, the ADSL standard allows only one pair of modems (COand RT) to communicate over a loop at the same time. The CO modem maysend a downstream signal while simultaneously receiving an upstreamsignal from the RT, frame by frame. Similarly, the RT modem may receivethe downstream communication from the CO modem and simultaneously sendupstream communication signals to the CO modem.

Since the standardization of ADSL communications, there have beenintroduced varied implementations and customized uses of the ADSLtechnology, such as disclosed in commonly assigned U.S. Pat. No.5,479,447 entitled “Method and Apparatus for Adaptive, VariableBandwidth, High-Speed Data Transmission of a Multi-Carrier Signal overDigital Subscriber Lines, the teachings of this patent included hereinby reference.

As homes and offices become more networked, there are typically multiplecommunication terminals and devices in the residential house or office,and local networks are likely installed to share resources, such asinternet access, printers, and so on. Home networks are particularlyunique in that cost and wiring issues are key considerations. The IEEE1394 standard has been recently developed which provides for data speedsup to hundreds Mbps. However, the IEEE 1394 standard also requiresspecial cabling for connection, and is not adapted to operate over thecommon twisted pair telephone lines wired typically throughout a home,for example. A new consortium of home networking, known as HomePhoneline Networking Alliance (HomePNA), was formed and headed by TutSystems and is supported by top computer and communication industryleaders including its founding members 3COM, AMD, AT&T, Compaq, HP, IBM,Intel, Lucent, and Rockwell, whereby Microsoft is one of the major stockholders of Tut Systems. HomePNA is able to connect PCs and peripheralswithin a household through a single pair phone line shared not only withthe telephone sets, but also with xDSL services provided by modemsexchanging information over the conventional twisted pair phone lines.HomePNA runs at the frequency range from 5.5 MHz to 9.5 MHz, while thePlain Old Telephone Service (POTS) operates in the frequency range under4 KHz, and the xDSL service operates at the frequency range from 275 KHzto 1 MHz. The current available HomePNA technology can provide 1 MbpsEthernet local networking, and may reach 10 Mbps in the near future.

SUMMARY OF THE INVENTION

The present invention achieves technical advantages as a Multi-ClientADSL Modem and network that can be configured as a home network byproviding multiple ADSL modems installed in different communicationterminals which may be connected to and coordinated by a multi-clientmodem at a central office serving as a network hub. This architectureallows connected PCs, for instance, to share internet access, printers,file storage, and so forth, but without extra hardware cost likeEthernet cards or upgraded cables. Each connection terminal, such as aPC, is able to communicate with the other as a home network bycommunicating over a single pair of twisted phone line conductors withthe central office (10) modem serving as a network hub. The presentinvention provides three sharing schemes allowing the multi-client ADSLmodems to communicate with the central office, and to communicate witheach other through the standard phone line connection. The sharingschemes include frame multiplexing, tone sharing, and code division.

In the frame multiplexing architecture, all connected multi-client ADSLmodems receive the same downstream signal from the CO modem. Eachmulti-client ADSL modem takes the data package itself asked. Eachmulti-client ADSL modem is allowed in schedule to send one or moreframes to the CO modem, while the other multi-client ADSL modems keepquiet. This CO modem can return the frame data from one multi-clientADSL modem to another multi-client ADSL modem through downstreamchannels. One of the multi-client ADSL modems is first connected to theCO modem, and is then configured as the master multi-client ADSL modem.This master multi-client ADSL modem maintains the superframetransmission if other multi-client ADSL modems join in, one afteranother.

Using the tone sharing technique, all connected multi-client ADSL modemsreceive the same downstream signals from the CO modem. Each multi-clientADSL modem takes the data package itself asked, whereby eachmulti-client ADSL modem uses a number of upstream tones to the CO modemwhile other multi-client ADSL modems use different tones, and whichtones can be sent simultaneously. The CO modem can return the data fromone multi-client ADSL modem to another multi-client ADSL modem throughdownstream channels. One of the multi-client ADSL modems is firstconnected to the CO modem, and is then configured as the mastermulti-client ADSL modem. The master multi-client ADSL modem willmaintain the superframe transmission if other multi-client ADSL modemsjoin in, one after another.

Using the code division architecture, all connected multi-client ADSLmodems receive the same downstream signal from the CO modem. Eachmulti-client ADSL modem takes the data package itself asked. Eachmulti-client ADSL modem is set up to code its data with a special signedkey word, such as is used in CDMA wireless applications. The ADSL modemthen modulates the coded data in all frames and in all tones. The COmodem can decode the data and re-send the data back to othermulti-client ADSL modems through downstream channels.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram configuration of two multi-client ADSL modemslocated within a single residence and each communicating over a singletwisted pair phone line to a remote single CO modem for communicationwith one another, or for communication between either RT modem and theCO modems;

FIG. 2 is a block diagram of a multi-client ADSL system, wherebymulti-client ADSL modems each communicate with the central office (CO)modem through one loop carrier comprising a single pair of twistedconductors;

FIG. 3A and FIG. 3B are graphs depicting how the multi-client modemsshare one upstream channel by frame multiplexing and tone division; and

FIG. 4 illustrates a method of initializing the multi-client ADSL modemswith one becoming the master modem maintaining the superframe.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to FIG. 1, there is shown at 10 a multi-client ADSLnetwork including a central office (CO) 12 having a CO modem 14connected via a single twisted pair loop of telephone conductors 16 toremote terminal (RT) modems 18. The CO modem 14 is adapted to serve oneor more respective communication terminals 20, which may be a landlinephone, computer, or wireless communication device. The respective RTmodems 18 are adapted to serve respective communication terminals 22such as PC, wireline phone, or wireless communication terminals such asa personal digital assistant (PDA). Also shown is a standard telephone24 also connected to and communicating over the single loop carrier 16for providing voice communications with remote terminals served by thecentral office 12. In this multi-client modem configuration 10, the RTterminals 22, which may be PCs, can not only access internetcommunications through the network via resources at the CO 12, but canalso communicate at a common site 26 with each other as a local homenetwork or an office-network.

Referring to FIG. 2, there is depicted in more detail the network 10 ofFIG. 1 which provides regular ADSL communication service between theresidential client modems 18 depicted as ATU-R, via the single loopcarrier 16 and the CO modem 14 identified as ATU-C. Both the CO modem 14and the RT modems 18 are equipped with frequency splitters and networkresources 30, each splitter comprising a high pass filter 32 and a lowpass filter 34. The high pass filter 32 and the low pass filter 34 eachseparate the ADSL frequency band communications from the voice frequencyband communications. Thus, a telephone set, voice band modem, or ISDNterminal, such as shown at 36, can communicate with a narrowband network38 via a single loop carrier 16, as shown. Likewise, the high passfilters 32 facilitate communication between customer premise networks 40via loop carrier 16 with a broadband network 42.

Depicted at 44 is the common single twisted pair of telephone lineextending between the remote terminal modems 18, such as in a daisychain arrangement from outlet to outlet within a home. Each of these RTmodems 18 is connected to and communicates through the respective highpass filter 32 of the splitter at the home. The ADSL servicecommunicating between customer premise network 40 and broadband network42 provides broadband network service to each home communication devicein the home network. The voice band communications provide regular PlainOld Telephone Service (POTS) or ISDN telephony service.

The multi-client ADSL system 10 allows each of the multiple clientmodems 18 to operate on the same single pair of twisted conductor phoneline routed through a home or office to communicate with and through asingle CO modem 14, simultaneously. No additional equipment or specialwiring is needed. Rather, the internal phone line throughout the home isused. With the multi-client ADSL system 10, the remote communicationterminals, which are depicted as a customer premise network 40 in FIG.2, can be locally networked without additional hardware cards, orspecial wiring such as CAT-5 wiring. The PCs 22 at the residential site26 can access the internet through the network 10 via the resources atthe CO 12, but can also communicate with each other as a local officenetwork or a home network.

Referring now to FIG. 3A and FIG. 3B, the multi-client modems 18 servingthe respective remote terminals 22 can be adapted to share the upstreamcommunications by sending data from the RT modem 18 to the CO modem 14using frequency division (sharing tones), by time division (sharingframes), or even applying code division like signatures similar to CDMAin wireless communications.

In frequency division, as shown in FIG. 3A, each multi-client modem 18is assigned unique tones for use on upstream channels. In time division,as shown in FIG. 3B, each multi-client modem 18 utilizes some frames onthe upstream channels while the other modems are keeping quiet.Alternatively, code division allows the multi-client modems 18 to senddata on upstream channels simultaneously to the CO modem 14, coveringall frames and all tones.

On downstream channels, each multi-client modem 18 receives all the datapackets from CO modem 14, but is also adapted to ascertain the datapackets that it has requested. A data packet has certain informationbits that shows its destination, and which information bits such asheader bits are used by each RT modem 18 to identify and decipher theassociated data therewith to determine if the data is to be interpreted.One of the multi-client ADSL modems 18 is first connected to the COmodem 14 and is responsively configured by the CO modem 14 as the mastermulti-client ADSL modem 18. This identified master multi-client ADSLmodem 18 then maintains the superframe transmission if othermulti-client ADSL modems 18 join in, one after another. This superframeis not shared by other multi-client ADSL modems.

Now referring to FIG. 4, there is illustrated at 60 a methodology bywhich the client modems 18 are initialized for use in the multi-clientmodem network 10, as shown in FIG. 1 and FIG. 2. The multi-client ADSLsystem 10 is compliant to the single client ADSL system when only oneclient modem 18 is connected to the loop carrier 16 comprising a singlephone line.

The system 10 first enters into the single modem state at step 62,similar to a normal ADSL system. Next, at step 64, if there is a secondmodem 18 initialized and turned on, this new added modem 18 requests forconnection by signaling the CO modem 14 with a special handshakingmessage exchange. The CO modem 14 responds to this request by informingthe first modem 18 to skip transmitting some frames in a time divisionimplementation, or some tones in a frequency division implementation.The CO modem 14 then provides for the first modem 18 to be re-trained asnecessary at step 66. The CO modem 14 informs the first RT modem 18 tobe the master modem of the multi-client operation and drops some frames.

At step 68, after re-setup of the first modem 18, the CO modem 14 willacknowledge and start a training process for the second modem wherebythe second modem 18 shares the dropped frames. The non-master clientmodem 18 does not generate the sync frame, which is generated by themaster client modem 18 only.

At step 70, if the set-up is ready, the system 10 enters themulti-client modem state, whereby one CO modem 14 communicates with themultiple RT client modems 18 through the single pair of phone line 16known as loop carrier. If at step 70 the set-up of the system is notready, the system returns back to step 66. When two or more clientmodems 18 are joining the single pair phone line 16, the CO modem 14 canre-train the first two modems 14, release more frames or tones for thenewly requesting modem 18, then set up the other.

In summary, the present invention provides a local home or officenetwork by which multiple remote terminals at a residential location oroffice can communicate with one another over a single common pair phoneline, without requiring special equipment or additional wiring. Thecentral office modem 14 operates as a network hub to routecommunications from one remote terminal to another while may all residewithin a common location, providing ADSL service over a single pair ofphone line. One remote terminal may communicate with the other, one at atime, or simultaneously depending on the architecture used. The regulartelephone service communicating voiceband signals is not affected.Splitters are used to separate the high frequency signals of ADSL fromthe low frequency signals for voice communications. The presentinvention utilizes ADSL communications that conform to ADSL standards.

Though the invention has been described with respect to a specificpreferred embodiment, many variations and modifications will becomeapparent to those skilled in the art upon reading the presentapplication. It is therefore the intention that the appended claims beinterpreted as broadly as possible in view of the prior art to includeall such variations and modifications.

1. A communication network, comprising: a network node; a first terminalhaving a first modem connected to said network node via a mastercommunication loop; and a second terminal having a second modem alsoconnected to said network node via said master communication loop,wherein said first and second terminals are adapted to communicate withsaid network node and each other with signals compatible with ADSLstandards.
 2. The communication network as specified in claim 1 whereinsaid first terminal and said second terminal are locally proximate oneanother.
 3. The communication network as specified in claim 2 whereinsaid master communication loop comprises a twisted pair of conductors.4. The communication network as specified in claim 2 wherein saidnetwork node is adapted to permit and enable said first terminal tocommunicate with said second terminal via said network node.
 5. Thecommunication network as specified in claim 4 wherein said firstterminal initiating a communication with said second terminal maintainsa superframe.
 6. The communication network as specified in claim 5wherein said network node directs said first terminal to maintain thesuperframe.
 7. The communication network as specified in claim 1 whereinsaid first terminal and said second terminal are adapted tosimultaneously communicate over said common master communication loopwith said network node.
 8. The communication network as specified inclaim 1 wherein each said first terminal and said second terminal areadapted to communicate over said common master communication loop usinga technique selected from the group consisting of: time division,frequency division, and code division.
 9. The communication network asspecified in claim 2 wherein said network node is a central office (CO)located remote from both said first and second terminal.
 10. Thecommunication network as specified in claim 1 wherein said firstterminal is a personal computer
 11. A modem adapted for use at a networknode, comprising; a transceiver adapted to communicate information witha remote first terminal over a master communication loop with signalscompatible with ADSL standards, wherein said transceiver is furtheradapted to communicate with a second remote terminal over said samemaster communication loop with signals compatible with ADSL standards.12. The modem as specified in claim 11 wherein said first and secondterminals are adapted to be co-located, said modem being adapted tofacilitate communications between each said terminal over said commonmaster communication loop.
 13. The modem as specified in claim 12wherein said master communication loop comprises a twisted pair ofconductors.
 14. The modem as specified in claim 12 wherein said modemestablishes said first terminal initiating a communication as a mastermaintaining a superframe.
 15. The modem as specified in claim 14 whereinsaid modem is adapted to simultaneously communicate with said firstterminal and said second terminal.
 16. The modem as specified in claim15 wherein said modem facilitates said simultaneous communication usinga technique selected from the group consisting of: time division, framedivision and code division.
 17. A method of communicating signalscompatible with ADSL standards over a communication network comprising:a network node; a first terminal having a first modem connected to saidnetwork node via a master communication loop; a second terminal having asecond modem also connected to said network node via said mastercommunication loop, wherein said first and second terminals are adaptedto communicate with said network node and each other with signalscompatible with ADSL standards; comprising the steps of: said firstterminal initiating a communication towards said second terminal viasaid common master communication loop; and said network node directingsaid first terminal to maintain a superframe.
 18. The method asspecified in claim 17 further comprising the step of said network nodefacilitating said communication between said first terminal and saidsecond terminal using a technique selected from the group consisting of:time division, frame division, and code division.
 19. The method asspecified in claim 17 wherein said master communication loop comprises asingle twisted pair of conductors.
 20. The method as specified in claim17 wherein said network node facilitates simultaneous communicationsbetween said first terminal and said second terminal over said mastercommunication loop.